Online monitoring of the distributed lateral displacement in large AC power generators using a high spatial resolution Brillouin optical fiber sensor

We report for the first time, to the best of our knowledge, online monitoring of the distributed lateral displacement in large AC power generators using high spatial resolution differential pulse-width pair Brillouin optical time-domain analysis (DPP-BOTDA). To perform the measurement of distributed lateral displacements with periods of only a few cm in large AC power generators, a 2cm spatial resolution strain measurement is realized using the differential pulse pair of 8/8.2 ns in DPP-BOTDA, and then the lateral displacements are reconstructed according to the strain-displacement relation with the assumption of a sine shape function. Using different fiberglass ripple springs, two types of lateral displacement with periods of 3 and 3.25cm are demonstrated, obtaining a maximum displacement of 0.43mm with a measurement accuracy of ∼ 40νm. This provides the information on the stator coil tightness through online monitoring of the distributed lateral displacement caused by the fiberglass ripple springs, and ensures safe operating conditions for large AC power generators. In addition, the large number of sensing points associated with distributed optical fiber sensors make it economically and technically practical to monitor large numbers of key components in a generator without any interference from the large magnetic and electrical fields.